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Topological Constraint on Chain-Folding Structure of Semicrystalline Polymer

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2019, Master of Science, University of Akron, Polymer Science.
Morphological observation of polymer crystals has been used as a structural probe of polymer crystallization. It has been long controversial that how the chain-folding (CF) structure is related to morphologies in polymer crystals. In this thesis, 13C-13C double-quantum (DQ) NMR, Atomic force microscopy (AFM), and polarized optical microscope (POM) were used to investigate a mean value of successive chain-folding number n of the CF structure and morphologies of 13C CH3-labeled isotactic-poly(1-butene) (iPB1) with a weight-averaged molecular weight Mw = 145K g/mol in solution- -grown crystals as a function of crystallization temperature (Tc) and polymer concentration (c) of 0.005 – 10 wt %, and in the melt-grown crystals as a function of Tc. Atomic force microscopy (AFM) revealed that iPB1 forms well-defined hexagonal single crystals and circular crystals from the very diluted solution (0.03 wt %) at Tc = 70 and ~0 °C. These morphological change is well known as kinetic effect at ~ m scale. With increasing polymer concentration, it was found that morphology changes from hexagonal to circulated crystals even at the high Tc and rapid quenching leads to the circulated crystals. Optical microscope revealed that nucleation densities and spherulite sizes increase and decreases, respectively, with decreasing Tc from 100, to 70 and ~0 °C. Comparisons of the DQ experiment result and spin dynamic simulation indicates that, the solution- and melt-grown crystals possessed adjacent re-entry structures which were invariant as a function of Tc, whereas variant as a function of concentration. The adjacent re-entry structures in a very dilute solution (c=0.005wt%) exhibited a long-range order (n ≥ 20) under the assumption of a single layer model compared with that in the melt states (n ~ 1.4). These results demonstrated that the concentration and entanglement of polymers are of significance in the CF process and structural formation during the crystallization initial stage. while kinetics does not. Meanwhile, The morphological and molecular-level structural results demonstrated that kinetics largely influences morphology, but it does not affect the molecular-level structure during crystallization.
Toshikazu Miyoshi (Advisor)
Mesfin Tsige (Committee Member)
58 p.

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Citations

  • Wang, K. (2019). Topological Constraint on Chain-Folding Structure of Semicrystalline Polymer [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555613375699697

    APA Style (7th edition)

  • Wang, Kun. Topological Constraint on Chain-Folding Structure of Semicrystalline Polymer. 2019. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1555613375699697.

    MLA Style (8th edition)

  • Wang, Kun. "Topological Constraint on Chain-Folding Structure of Semicrystalline Polymer." Master's thesis, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555613375699697

    Chicago Manual of Style (17th edition)